1. Field of the Invention
This invention relates to an innovative hydraulic grip control unit provided with independent gripping arms driven hydraulically to seize a load. More generally, this invention relates to a grip including said innovative hydraulic control unit.
2. State of the Prior Art
The technique of realizing grips provided with two independent gripping arms driven hydraulically to seize a load while cooperating with an appropriate striker arm is known. Each gripping arm is driven by its own hydraulic cylinder. The two driving cylinders are fed in parallel by a hydraulic control unit which receives oil from a hydraulic pump and distributes it to the cylinders while controlling the force of the grip on the load.
At the point of the hydraulic circuit where the oil supply duct branches into the two branches of the cylinders, a flow divider intended to keep the apportionment of the fluid balanced between the two cylinders is inserted to obtain synchronism in the movement of the two gripping arms.
Said hydraulic units however do not ensure synchronism of the arms under all operating conditions of the grip. Indeed, when the system works with oil flows considerably lower than the nominal flow of the system the apportionment error committed by the divider becomes considerable and causes a lack of sync of the movement of the arms and especially during cylinder re-entry.
In addition, the use of a divider with high nominal flow equal to the nominal flow of the system considerably affects the total cost of the unit.
The general purpose of this invention is to remedy the above-mentioned shortcomings by making available a hydraulic grip control unit provided with distinct gripping arms capable of ensuring synchronism in the movement of the arms in all grip operating conditions.
Another purpose of this invention is to make available a control unit which would be economical and have flexible operation.